scholarly journals A venous-specific purinergic signaling cascade initiated by Pannexin 1 regulates TNFα-induced increases in endothelial permeability

2021 ◽  
Vol 14 (672) ◽  
pp. eaba2940 ◽  
Author(s):  
Daniela Maier-Begandt ◽  
Heather Skye Comstra ◽  
Samuel A. Molina ◽  
Nenja Krüger ◽  
Claire A. Ruddiman ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Barrier Function ◽  
Ex Vivo ◽  
Purinergic Signaling ◽  
Cecal Ligation ◽  
Endothelial Permeability ◽  
Pannexin 1 ◽  
Rna Expression Profiling ◽  
Transendothelial Permeability ◽  
Arterial Endothelium

The endothelial cell barrier regulates the passage of fluid between the bloodstream and underlying tissues, and barrier function impairment exacerbates the severity of inflammatory insults. To understand how inflammation alters vessel permeability, we studied the effects of the proinflammatory cytokine TNFα on transendothelial permeability and electrophysiology in ex vivo murine veins and arteries. We found that TNFα specifically decreased the barrier function of venous endothelium without affecting that of arterial endothelium. On the basis of RNA expression profiling and protein analysis, we found that claudin-11 (CLDN11) was the predominant claudin in venous endothelial cells and that there was little, if any, CLDN11 in arterial endothelial cells. Consistent with a difference in claudin composition, TNFα increased the permselectivity of Cl− over Na+ in venous but not arterial endothelium. The vein-specific effects of TNFα also required the activation of Pannexin 1 (Panx1) channels and the CD39-mediated hydrolysis of ATP to adenosine, which subsequently stimulated A2A adenosine receptors. Moreover, the increase in vein permeability required the activation of the Ca2+ channel TRPV4 downstream of Panx1 activation. Panx1-deficient mice resisted the pathologic effects of sepsis induced by cecal ligation and puncture on life span and lung vascular permeability. These data provide a targetable pathway with the potential to promote vein barrier function and prevent the deleterious effects of vascular leak in response to inflammation.

scholarly journals Metformin-stimulated AMPK-α1 promotes microvascular repair in acute lung injury

2013 ◽  
Vol 305 (11) ◽  
pp. L844-L855 ◽  
Author(s):  
Ming-Yuan Jian ◽  
Mikhail F. Alexeyev ◽  
Paul E. Wolkowicz ◽  
Jaroslaw W. Zmijewski ◽  
Judy R. Creighton
Keyword(s):  
Endothelial Cells ◽  
Acute Lung Injury ◽  
Lung Injury ◽  
Ex Vivo ◽  
Endothelial Permeability ◽  
Beneficial Effects ◽  
Isolated Lung

Acute lung injury secondary to sepsis is a leading cause of mortality in sepsis-related death. Present therapies are not effective in reversing endothelial cell dysfunction, which plays a key role in increased vascular permeability and compromised lung function. AMP-activated protein kinase (AMPK) is a molecular sensor important for detection and mediation of cellular adaptations to vascular disruptive stimuli. In this study, we sought to determine the role of AMPK in resolving increased endothelial permeability in the sepsis-injured lung. AMPK function was determined in vivo using a rat model of endotoxin-induced lung injury, ex vivo using the isolated lung, and in vitro using cultured rat pulmonary microvascular endothelial cells (PMVECs). AMPK stimulation using N1-(α-d-ribofuranosyl)-5-aminoimidizole-4-carboxamide or metformin decreased the LPS-induced increase in permeability, as determined by filtration coefficient ( Kf) measurements, and resolved edema as indicated by decreased wet-to-dry ratios. The role of AMPK in the endothelial response to LPS was determined by shRNA designed to decrease expression of the AMPK-α1 isoform in capillary endothelial cells. Permeability, wounding, and barrier resistance assays using PMVECs identified AMPK-α1 as the molecule responsible for the beneficial effects of AMPK in the lung. Our findings provide novel evidence for AMPK-α1 as a vascular repair mechanism important in the pulmonary response to sepsis and identify a role for metformin treatment in the management of capillary injury.

scholarly journals BMX Represses Thrombin-PAR1–Mediated Endothelial Permeability and Vascular Leakage During Early Sepsis

2020 ◽  
Vol 126 (4) ◽  
pp. 471-485 ◽  
Author(s):  
Zhao Li ◽  
Mingzhu Yin ◽  
Haifeng Zhang ◽  
Weiming Ni ◽  
Richard W. Pierce ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Cecal Ligation ◽  
Endothelial Permeability ◽  
Vascular Leakage ◽  
Lung Epithelial Cells ◽  
Negative Regulator ◽  
Cecal Ligation And Puncture ◽  
Early Sepsis

Rationale: BMX (bone marrow kinase on the X chromosome) is highly expressed in the arterial endothelium from the embryonic stage to the adult stage in mice. It is also expressed in microvessels and the lymphatics in response to pathological stimuli. However, its role in endothelial permeability and sepsis remains unknown. Objective: We aimed to delineate the function of BMX in thrombin-mediated endothelial permeability and the vascular leakage that occurs with sepsis in cecal ligation and puncture models. Methods and Results: The cecal ligation and puncture model was applied to WT (wild type) and BMX-KO (BMX global knockout) mice to induce sepsis. Meanwhile, the electric cell-substrate impedance sensing assay was used to detect transendothelial electrical resistance in vitro and, the modified Miles assay was used to evaluate vascular leakage in vivo. We showed that BMX loss caused lung injury and inflammation in early cecal ligation and puncture–induced sepsis. Disruption of BMX increased thrombin-mediated permeability in mice and cultured endothelial cells by 2- to 3-fold. The expression of BMX in macrophages, neutrophils, platelets, and lung epithelial cells was undetectable compared with that in endothelial cells, indicating that endothelium dysfunction, rather than leukocyte and platelet dysfunction, was involved in vascular permeability and sepsis. Mechanistically, biochemical and cellular analyses demonstrated that BMX specifically repressed thrombin-PAR1 (protease-activated receptor-1) signaling in endothelial cells by directly phosphorylating PAR1 and promoting its internalization and deactivation. Importantly, pretreatment with the selective PAR1 antagonist SCH79797 rescued BMX loss-mediated endothelial permeability and pulmonary leakage in early cecal ligation and puncture–induced sepsis. Conclusions: Acting as a negative regulator of PAR1, BMX promotes PAR1 internalization and signal inactivation through PAR1 phosphorylation. Moreover, BMX-mediated PAR1 internalization attenuates endothelial permeability to protect vascular leakage during early sepsis.

scholarly journals HIV gp120 Protein Increases the Function of Connexin 43 Hemichannels and Pannexin-1 Channels in Astrocytes: Repercussions on Astroglial Function

2020 ◽  
Vol 21 (7) ◽  
pp. 2503 ◽  
Author(s):  
Rosario Gajardo-Gómez ◽  
Cristian A. Santibañez ◽  
Valeria C. Labra ◽  
Gonzalo I. Gómez ◽  
Eliseo A. Eugenin ◽  
...  
Keyword(s):  
Connexin 43 ◽  
Molecular Mechanisms ◽  
Ex Vivo ◽  
Purinergic Signaling ◽  
Atp Release ◽  
P38 Map Kinase ◽  
Motor Deficits ◽  
Pannexin 1 ◽  
Channel Opening ◽  
Wide Range

At least half of human immunodeficiency virus (HIV)-infected individuals suffer from a wide range of cognitive, behavioral and motor deficits, collectively known as HIV-associated neurocognitive disorders (HAND). The molecular mechanisms that amplify damage within the brain of HIV-infected individuals are unknown. Recently, we described that HIV augments the opening of connexin-43 (Cx43) hemichannels in cultured human astrocytes, which result in the collapse of neuronal processes. Whether HIV soluble viral proteins such as gp120, can regulate hemichannel opening in astrocytes is still ignored. These channels communicate the cytosol with the extracellular space during pathological conditions. We found that gp120 enhances the function of both Cx43 hemichannels and pannexin-1 channels in mouse cortical astrocytes. These effects depended on the activation of IL-1β/TNF-α, p38 MAP kinase, iNOS, cytoplasmic Ca2+ and purinergic signaling. The gp120-induced channel opening resulted in alterations in Ca2+ dynamics, nitric oxide production and ATP release. Although the channel opening evoked by gp120 in astrocytes was reproduced in ex vivo brain preparations, these responses were heterogeneous depending on the CA1 region analyzed. We speculate that soluble gp120-induced activation of astroglial Cx43 hemichannels and pannexin-1 channels could be crucial for the pathogenesis of HAND.

Abstract 45: Endothelial Aryl Hydrocarbon Receptor Nucleatranslator (Arnt) is a Novel Regulator of Cardiac Endothelial Barrier Integrity in Diabetes

2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Maura Knapp ◽  
Mei Zheng ◽  
Nikola Sladojevic ◽  
Qiong Zhao ◽  
Konstaintin G Birukov ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Barrier Function ◽  
Endothelial Permeability ◽  
Endothelial Barrier ◽  
Endothelial Barrier Function ◽  
Barrier Dysfunction ◽  
Endothelial Barrier Dysfunction ◽  
Aryl Hydrocarbon ◽  
Underlying Mechanisms

Background: Diabetes leads to endothelial barrier dysfunction and altered endothelial permeability, which results in increased cardiovascular risk. ARNT, also known as HIF-1β, a transcription factor that functions as a master regulator of glucose homeostasis, has been implicated in diabetes. Endothelial-specific ARNT deletion (ArntΔEC) in mice is embryonically lethal, with hemorrhage occurring in the heart during the embryonic stage. However, the particular role of endothelial ARNT(ecARNT) in diabetes is largely unknown. We have found a significant decrease in ARNT expression in both diabetic rodent endothelial cells and diabetic human hearts. We hypothesize that a loss of ecARNT mediates endothelial barrier dysfunction during diabetes. Methods and Results: We generated inducible endothelial specific ARNT knockout mice (ecARNT-/-) by crossing mice with loxP sequences flanking exon 6 of ARNT with Cre ERT2 mice under the VE-cadherin promoter. A 90% deletion of ecARNT was achieved following two weeks of oral tamoxifen administration. ecARNT-/- mice exhibit severe blood vessel leakage, which is restricted to the heart, suggesting a distinct function for ecARNT in different tissues. Cardiomyopathy is evident 6 months after ARNT deletion. In vitro , trans-endothelial electrical resistance (TER) and transwell assays have confirmed endothelial barrier disruption in cardiac microvascular endothelial cells (CMEC) isolated from both ecARNT-/- hearts and diabetic (DB/DB) mouse hearts. To determine the underlying mechanisms by which ARNT may regulate endothelial barrier function, we performed DNA sequencing on CMEC isolated from control, ecARNT-/-, and DB/DB mice. Data suggest a significant increase in TNFa signaling, including ELAM-1 and ICAM-1 in CMEC isolated from ecARNT-/- CMEC and diabetic CMEC. Moreover, use of anti-TNFa antibody rescues endothelial barrier dysfunction in CMEC isolated from ecARNT-/- mice. Taken together, these results suggest that a reduction in ecARNT during diabetes may mediate endothelial barrier dysfunction through a TNFa signaling pathway. Conclusion: ecARNT is a critical mediator of endothelial barrier function and could potentially serve as a therapeutic target for diabetic cardiovascular diseases.

scholarly journals Activation of P2X7 and P2Y11 purinergic receptors inhibits migration and normalizes tumor-derived endothelial cells via cAMP signaling

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
D. Avanzato ◽  
T. Genova ◽  
A. Fiorio Pla ◽  
M. Bernardini ◽  
S. Bianco ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Breast Carcinoma ◽  
Purinergic Receptors ◽  
Purinergic Signaling ◽  
Endothelial Permeability ◽  
Human Tumor ◽  
Human Breast Carcinoma ◽  
Human Breast ◽  
Migratory Activity

AbstractPurinergic signaling is involved in inflammation and cancer. Extracellular ATP accumulates in tumor interstitium, reaching hundreds micromolar concentrations, but its functional role on tumor vasculature and endothelium is unknown. Here we show that high ATP doses (>20 μM) strongly inhibit migration of endothelial cells from human breast carcinoma (BTEC), but not of normal human microvascular EC. Lower doses (1–10 μM) result ineffective. The anti-migratory activity is associated with cytoskeleton remodeling and is significantly prevented by hypoxia. Pharmacological and molecular evidences suggest a major role for P2X7R and P2Y11R in ATP-mediated inhibition of TEC migration: selective activation of these purinergic receptors by BzATP mimics the anti-migratory effect of ATP, which is in turn impaired by their pharmacological or molecular silencing. Downstream pathway includes calcium-dependent Adenilyl Cyclase 10 (AC10) recruitment, cAMP release and EPAC-1 activation. Notably, high ATP enhances TEC-mediated attraction of human pericytes, leading to a decrease of endothelial permeability, a hallmark of vessel normalization. Finally, we provide the first evidence ofin vivoP2X7R expression in blood vessels of murine and human breast carcinoma. In conclusion, we have identified a purinergic pathway selectively acting as an antiangiogenic and normalizing signal for human tumor-derived vascular endothelium.

scholarly journals Endothelial pannexin 1 channels control inflammation by regulating intracellular calcium

2019 ◽  
Author(s):  
Yang Yang ◽  
Leon Delalio ◽  
Angela K Best ◽  
Edgar Macal ◽  
Jenna Milstein ◽  
...  
Keyword(s):  
Cardiovascular Disease ◽  
Endothelial Cells ◽  
Plasma Membrane ◽  
Intracellular Calcium ◽  
Tumor Necrosis ◽  
Purinergic Signaling ◽  
Flow Cytometric Analysis ◽  
Atp Release ◽  
Pannexin 1 ◽  
Intracellular Ca

In BriefInterleukine-1 beta (IL-1β) has been identified as a critical factor that contributes to the inflammatory response in cardiovascular disease (e.g., atherosclerosis). Pannexin 1 (Panx1) channel activity in endothelial cells regulates localized inflammatory cell recruitment. In response to prolonged tumor necrosis factor alpha (TNF) treatment, Yang et al. found that the Panx1 channel is targeted to the plasma membrane, where it facilitates an increase in intracellular calcium to control the production and release of cytokines including IL-1β.GRAPHICAL ABSTRACTAbstractThe proinflammatory cytokine IL-1β is a significant risk factor in cardiovascular disease that can be targeted to reduce major cardiovascular events. IL-1β expression and release are tightly controlled by changes in intracellular Ca2+. In addition, purinergic signaling through ATP release has also been reported to promote IL-1β production. Despite this, the mechanisms that control IL-1β synthesis and expression have not been identified. The pannexin 1 (Panx1) channel has canonically been implicated in ATP release, especially during inflammation. However, resolution of purinergic signaling occurs quickly due to blood flow and the presence of ectonucleotidases. We examined Panx1 in human endothelial cells following treatment with the pro-inflammatory cytokine tumor necrosis alpha (TNF). In response to long-term TNF treatment, we identified a dramatic increase in Panx1 protein expression at the plasma membrane. Analysis by whole transcriptome sequencing (RNA-seq), qPCR, and treatment with specific kinase inhibitors, revealed that TNF signaling induced NFκβ-associated Panx1 transcription. Genetic inhibition of Panx1 reduced the expression and secretion of IL-1β. We initially hypothesized that increased Panx1-mediated ATP release acted in a paracrine fashion to control cytokine expression. However, our data demonstrate that IL1-β expression was not altered after direct ATP stimulation, following degradation of ATP by apyrase, or after pharmacological blockade of P2 receptors. These data suggest that non-purinergic pathways, involving Panx1, control IL-1β production. Because Panx1 forms a large pore channel, we hypothesized it may act to passively diffuse Ca2+ into the cell upon opening to regulate IL-1β. High-throughput flow cytometric analysis demonstrated that TNF treatments lead to elevated intracellular Ca2+. Genetic or pharmacological inhibition of Panx1 reduced TNF-associated increases in intracellular Ca2+, and IL-1β transcription. Furthermore, we found that the Ca2+-sensitive NFκβ-p65 protein failed to localize to the nucleus after genetic or pharmacological block of Panx1. Taken together, our study provides the first evidence that intracellular Ca2+ regulation via the Panx1 channel induces a feed-forward effect on NFκβ to regulate IL-1β synthesis and release in endothelium during inflammation.

Phosphorylation of endothelial nitric oxide synthase by atypical PKCζ contributes to angiopoietin-1–dependent inhibition of VEGF-induced endothelial permeability in vitro

Blood ◽  
2009 ◽  
Vol 114 (15) ◽  
pp. 3343-3351 ◽  
Author(s):  
Malika Oubaha ◽  
Jean-Philippe Gratton
Keyword(s):  
Nitric Oxide ◽  
Endothelial Cells ◽  
Endothelial Permeability ◽  
No Production ◽  
No Release ◽  
Dependent Inhibition ◽  
Transendothelial Permeability ◽  
Endothelial Nitric Oxide ◽  
Angiopoietin 1

Abstract Vascular endothelial growth factor (VEGF) is a potent angiogenic cytokine that also increases vascular permeability. Nitric oxide (NO) released from endothelial cells, after activation of endothelial NO synthase (eNOS), contributes to proangiogenic and permeability effects of VEGF. Angiopoietin-1 (Ang-1), via Tie2 receptors, shares many of the proangiogenic properties of VEGF on endothelial cells. However, in contrast to VEGF, Ang-1 protects blood vessels from increased plasma leakage, which contributes to their stabilization. Because eNOS-derived NO is central to increased permeability in response to VEGF, we investigated whether Ang-1 interferes with VEGF signaling to eNOS. We demonstrate that Ang-1 stimulation of endothelial cells inhibits VEGF-induced NO release and transendothelial permeability. In contrast to VEGF stimulation, Ang-1 causes a marked protein kinase C (PKC)–dependent increase in phosphorylation of eNOS on the inhibitory Thr497. Furthermore, using pharmacologic inhibitors, overexpression studies, and small interfering RNA-mediated gene silencing, we demonstrate that atypical PKCζ is responsible for phosphorylation of eNOS on Thr497 in response to Ang-1. In addition, PKCζ knockdown abrogates the capacity of Ang-1 to inhibit VEGF-induced NO release and endothelial permeability. Thus, inhibition of NO production by Ang-1, via phosphorylation of eNOS on Thr497 by PKCζ, is responsible, at least in part, for inhibition of VEGF-stimulated endothelial permeability by Ang-1.

Regulation of bovine brain microvascular endothelial tight junction assembly and barrier function by laminar shear stress

2007 ◽  
Vol 292 (6) ◽  
pp. H3190-H3197 ◽  
Author(s):  
Olga C. Colgan ◽  
Gail Ferguson ◽  
Nora T. Collins ◽  
Ronan P. Murphy ◽  
Gerardeane Meade ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Tight Junction ◽  
Barrier Function ◽  
Bovine Brain ◽  
Steady Shear ◽  
Microvascular Endothelial Cells ◽  
Pulsatile Shear Stress ◽  
Microvascular Endothelial ◽  
Transendothelial Permeability

Blood-brain barrier (BBB) controls paracellular solute diffusion into the brain microenvironment and is maintained primarily by tight junctions between adjacent microvascular endothelial cells. Studies implicate blood flow-associated shear stress as a pathophysiological mediator of BBB function, although detailed biochemical data are scarce. We hypothesize that shear stress upregulates BBB function via direct modulation of expression and properties of pivotal tight-junction proteins occludin and zonula occludens-1 (ZO-1). Bovine brain microvascular endothelial cells (BBMvECs) were exposed to either steady or pulsatile shear stress (10 and 14 dyn/cm2, respectively) for 24 h. Sheared BBMvECs were monitored for occludin-ZO-1 expression, association, and subcellular localization, and transendothelial permeability of BBMvECs to FITC-dextran and 14[C]sucrose was assessed. Actin reorganization and BBMvEC realignment were observed following steady shear stress for 24 h. Substantial increases in occludin mRNA and protein expression (2.73 ± 0.26- and 1.83 ± 0.03-fold) and in occludin-ZO-1 association (2.12 ± 0.15-fold) were also observed. Steady shear stress also induced clear relocalization of both proteins to the cell-cell border in parallel with reduced transendothelial permeability to FITC-dextran (but not sucrose). Following pulsatile shear stress, increased protein levels for both occludin and ZO-1 (2.15 ± 0.02- and 1.67 ± 0.21-fold) and increased occludin-ZO-1 association (2.91 ± 0.14-fold) were observed in parallel with a reduction in transendothelial permeability to 14[C]sucrose. Shear stress upregulates BBMvEC barrier function at the molecular level via modulation of expression, association, and localization of occludin and ZO-1. The pulsatile shear model appeared to give the most profound biochemical responses.

Site-specific thrombin receptor antibodies inhibit Ca2+ signaling and increased endothelial permeability

1997 ◽  
Vol 273 (5) ◽  
pp. C1756-C1763 ◽  
Author(s):  
Lan T. Nguyen ◽  
Hazel Lum ◽  
Chinnaswamy Tiruppathì ◽  
Asrar B. Malik
Keyword(s):  
Endothelial Cells ◽  
Clearance Rate ◽  
Endothelial Permeability ◽  
Receptor Activation ◽  
Thrombin Receptor ◽  
Acetoxymethyl Ester ◽  
Tethered Ligand ◽  
Albumin Clearance ◽  
Transendothelial Permeability ◽  
Loop 2

Thrombin receptor is activated by thrombin-mediated cleavage of the receptor’s NH2 terminus between Arg-41 and Ser-42, generating a new NH2terminus that functions as a “tethered ligand” by binding to sites on the receptor. We prepared antibodies (Abs) directed against specific receptor domains to study the tethered ligand-receptor interactions required for signaling the increase in endothelial permeability to albumin. We used polyclonal Abs directed against the peptide sequences corresponding to the extracellular NH2 terminus [residues 70–99 (AbDD) and 1–160 (AbEE)] and extracellular loops 1 and 2 [residues 161–178 (AbL1) and 244–265 (AbL2)] of the seven-transmembrane thrombin receptor. Receptor activation was determined by measuring changes in cytosolic Ca2+ concentration ([Ca2+]i) in human dermal microvascular endothelial cells (HMEC) loaded with Ca2+-sensitive fura 2-acetoxymethyl ester dye. The transendothelial125I-labeled albumin clearance rate (a measure of endothelial permeability) was determined across the confluent HMEC monolayers. AbEE (300 μg/ml), directed against the entire extracellular NH2-terminal extension, inhibited the thrombin-induced increases in [Ca2+]iand the endothelial 125I-albumin clearance rate (>90% reduction in both responses). AbDD (300 μg/ml), directed against a sequence within the NH2-terminal extension, inhibited 70% of the thrombin-induced increase in [Ca2+]iand 60% of the increased125I-albumin clearance rate. AbL2 (300 μg/ml) inhibited these responses by 70 and 80%, respectively. However, AbL1 (300 μg/ml) had no effect on either response. We conclude that NH2-terminal extension and loop 2 are critical sites for thrombin receptor activation in endothelial cells and thus lead to increased [Ca2+]iand transendothelial permeability to albumin.

scholarly journals Connexin Channels Provide a Target to Manipulate Brain Endothelial Calcium Dynamics and Blood—Brain Barrier Permeability

2011 ◽  
Vol 31 (9) ◽  
pp. 1942-1957 ◽  
Author(s):  
Marijke De Bock ◽  
Maxime Culot ◽  
Nan Wang ◽  
Mélissa Bol ◽  
Elke Decrock ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Blood Brain Barrier ◽  
Purinergic Signaling ◽  
Endothelial Permeability ◽  
Brain Barrier ◽  
In Vivo Experiments ◽  
Blood Brain ◽  
Novel Approach

The cytoplasmic Ca2+ concentration ([Ca2+]i) is an important factor determining the functional state of blood-brain barrier (BBB) endothelial cells but little is known on the effect of dynamic [Ca2+]i changes on BBB function. We applied different agonists that trigger [Ca2+]i oscillations and determined the involvement of connexin channels and subsequent effects on endothelial permeability in immortalized and primary brain endothelial cells. The inflammatory peptide bradykinin (BK) triggered [Ca2+]i oscillations and increased endothelial permeability. The latter was prevented by buffering [Ca2+]i with BAPTA, indicating that [Ca2+]i oscillations are crucial in the permeability changes. Bradykinin-triggered [Ca2+]i oscillations were inhibited by interfering with connexin channels, making use of carbenoxolone, Gap27, a peptide blocker of connexin channels, and Cx37/43 knockdown. Gap27 inhibition of the oscillations was rapid (within minutes) and work with connexin hemichannel-permeable dyes indicated hemichannel opening and purinergic signaling in response to stimulation with BK. Moreover, Gap27 inhibited the BK-triggered endothelial permeability increase in in vitro and in vivo experiments. By contrast, [Ca2+]i oscillations provoked by exposure to adenosine 5’ triphosphate (ATP) were not affected by carbenoxolone or Gap27 and ATP did not disturb endothelial permeability. We conclude that interfering with endothelial connexin hemichannels is a novel approach to limiting BBB-permeability alterations.

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